Re: Ethernet NIC dual homing

["H. Peter Anvin" <hpa@zytor.com>]

Followup to:  <p05100304b803c6908755@[10.128.7.49]>
By author:    Jonathan Lundell <jlundell@pobox.com>
In newsgroup: linux.dev.kernel
> >
> >It doesn't work to detect link state through bridging device (say, bridged
> >ethernet over T3). The T3 might go down, but your MII link to the local
> >router will remain "up", so you will never know about the loss of link and
> >your packets will happily go into the void...
> 
> ARP isn't going to do much for you once the failure is beyond the 
> local segment, is it?
> 

ARP is broadcast to the layer 2 local segment; link detection refers
to the layer 1 local segment, which is not necessarily the same.

On the other hand, doing link detection is extremely useful for a
portable computer: when I plug in my Ethernet cable in a portable
system I want it to try to start doing DHCP detection and anything
else that is normally associated with the interface being "up" at that
time.

	-hpa
-- 
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